Vaccination reduces risk for VTE among ambulatory patients with COVID-19
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Individuals who acquired COVID-19 infection not requiring hospitalization had greatly increased risk for incident venous thromboembolism, according to results of an English population-based cohort study.
However, being fully vaccinated against COVID-19 vastly reduced this risk among patients who developed breakthrough infections, the findings showed.
Researchers also identified several factors associated with increased risk for VTE after COVID-19 infection, including obesity, older age and male sex.
Background
Multiple hospital-based studies have shown associations of COVID-19 infection with increased risk for subsequent VTE, the investigators noted.
“We knew vaccines reduce the severity of COVID-19, therefore minimizing the risk of hospital admission for related pneumonia,” Dani Prieto-Alhambra, MD, MSc (Oxf), PhD, professor of pharmacoepidemiology at University of Oxford, told Healio. “We wanted to investigate whether the benefits of vaccination would go beyond this and also reduce the risk for post-COVID-19 thrombotic complications.”
Methodology
Prieto-Alhambra and colleagues conducted a population-based cohort analysis of 18,818 patients (mean age, 64.3 ± 8 years; 56% women) with outpatient COVID-19 who participated in the UK Biobank study. The analysis also included 93,179 matched uninfected control participants.
The investigation excluded patients with a history of VTE who used antithrombotic agents during the year before confirmed COVID-19 diagnosis.
Composite VTE — including deep vein thrombosis or pulmonary embolism — served as the study’s primary outcome.
Key findings
Investigators noted an increased risk for VTE at 30 days associated with COVID-19 infection, including an incidence rate per 1,000 person-years of 50.99 for those with COVID-19 infection vs. 2.37 for uninfected study subjects (HR = 21.42; 95% CI, 12.63-36.31).
Full vaccination against COVID-19 greatly reduced the risk for developing VTE (HR = 5.95; 95% CI, 1.82-19.5).
Investigators identified older age (adjusted HR per 10 years = 1.87; 95% CI, 1.5-2.33), male sex (HR = 1.69; 95% CI, 1.3-2.19) and obesity (HR = 1.83; 95% CI, 1.28-2.61) as independently associated with higher risk for developing VTE among patients with COVID-19.
Patients with inherited thrombophilia also demonstrated an increased risk for VTE after COVID-19 infection (HR = 2.05; 95% CI, 1.15-3.66).
Clinical implications
The results suggest vaccination can help prevent COVID-19-related VTE, according to Prieto-Alhambra.
“We saw a much lower risk for thrombosis post COVID-19 when subjects got the infection after full two-dose vaccination,” he told Healio. “Despite this, COVID-19 remains a condition that can lead to thrombotic complications, particularly among older males, those who are overweight and those with a genetic predisposition to thrombosis.”
For more information :
Dani Prieto-Alhambra, MD, PhD, can be reached at Botnar Research Centre, Windmill Road, OX37LD Oxford, UK; email: daniel.prietoalhambra@ndorms.ox.ac.uk.
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